1. Field of the Invention
The present invention concerns a device for non-contacting (contact-free) transmission of electrical signals between two gantry parts of a computed tomography system that can rotate relative to one another, wherein at least one annular, circumferential transmitter element to transmit the electrical signals is arranged on one gantry part, and at least one receiver element to receive the signals emitted by the transmitter element is arranged on the other gantry part.
2. Description of the Prior Art
It is generally known that, in computed tomography using CT systems with continuously rotating gantries, the necessity exists to transmit both electrical power and electrical signals between the stationary portion of a gantry and the rotating portion of a gantry. Large electrical outputs are normally transferred with the use of slip contacts while electrical signals (as they are used in data transmission of detector data or of timing signals) are transmitted with the use of contact-free data transmission.
For example, European Patent Application EP 1 337 001 A1 and U.S. Pat. No. 6,301,324 describe such systems for contact-free transmission of electrical signals.
In the transmission of electrical signals with high frequency, the problem frequently exists that a large (often unacceptably large) proportion of perturbing radiation arises in the transmission paths so that it is difficult to comply with legal requirements, in particular when the transferred data rate rises sharply.
A circumferential ring with a special conductor structure attached therein that forms two traces arranged in a mirror image is frequently used for contact-free data transmission. For data transmission, these two differential conductor traces are alternatingly charged with differently polarized voltages (for example +5 volts and −5 volts). One polarity corresponds to a binary zero while the opposite polarity corresponds to a binary one. If higher data rates are to be transmitted, multiple mirror-image conductor structure pairs are used in parallel, in part due to the limited transmission capacity of such a conductor structure pair. It has been shown that a disproportionately sharp rise of EMC radiation (perturbing radiation) unexpectedly occurs. It is surmised that the positioning of the conductor structure pairs on the circumferential base structure is the reason for the unexpected rise of EMC radiation.